The present invention is related to radar antennas in general, and more particularly, to an antenna assembly which is operative to rotate an antenna structure in azimuth to a predetermined angular orientation automatically as it is being retracted from its deployed state to its stowed state against the surface of the supporting structure thereof.
Some radar antennas, especially those of the type for application on-board aircraft, such as helicopters and the like, are generally mounted on a supporting structure, like the fuselage, for example, and are deployed away from the surface thereof during operation so that they may be rotated to scan in azimuth without contacting physically any protrusions from the surface of the supporting structure in the antenna's rotational path. In addition, prior to retraction to a stowed state, antennas of this type may be required to be rotated to a predetermined azimuth angle so that when retracted, the antenna structure is of an orientation to fit the contour of the surface portion of their supporting structure, which it is designed to rest against in the stowed state.
FIGS. 1 and 2 are cross-sectional illustrative views of an antenna assembly which is required to be maneuvered for retraction so that an antenna pod structure 10 thereof is properly oriented in azimuth against the fuselage of the aircraft in the stowed state. FIG. 1 illustrates the antenna assembly having its antenna structure 10 extended away from the external surface 12 of the aircraft in a deployed state. Structural members 14 constitute that portion of the aircraft which supports the overall antenna assembly. In the particular embodiment of FIGS. 1 and 2, the antenna structure 10 is coupled to a main drive shaft 16 utilizing a conventional coupling clamp 18. The main drive shaft 16 is disposed through a main drive housing 20 for alignment thereof during the extension and retraction translational movement. The translational movement through the main drive housing 20 is assisted by a recirculating ball spline 22 and associated ball spline grooves at 24. The main drive shaft 16 is guided along its translational axis for extension and retraction by a linear ball screw 26 and associated ball nuts 28 and thrust plate assembly 30. A flange 32 provides additional guidance along a predetermined cam follower guide path 34. A conventional rotary joint assembly 36 is provided in the top portion of the main drive shaft 16 and driven when engaged in the deployed state as shown in FIG. 1 by a conventional hydraulic drive mechanism 40. The hydraulic drive mechanism 40 may further be utilized for driving the antenna assembly between its deployed and stowed states (refer to FIGS. 1 and 2, respectively).
A waveguide flange 42 is disposed in a region on top of the drive shaft 16 to mate with a waveguide flange input 44 when the antenna assembly is in the deployed state as shown in FIG. 1.
In operation then, the antenna pod structure 10 is extended with a translational movement along the axis indicated by the double arrow 50 from its stowed state of FIG. 2 to its deployed state of FIG. 1 using the conventional guide assist mechanisms described hereabove. When in the deployed state, the rotary joint assembly 36 is engaged to the hydraulic drive assembly 40 to provide azimuth rotation of the antenna pod structure 10 angularly about the longitudinal axis 50 of the main drive shaft 16. Moreover, when in the deployed state, the waveguide input connection is mated at 42/44 to permit radar transmission and reception operation.
Now, prior to being retracted, the antenna pod structure 10 may be in a random azimuth angular orientation with respect to the supporting structure surface 12. Thus for retraction, the procedure requires that the antenna pod structure 10 be rotated, utilizing the hydraulic drive assembly 40 and rotary joint assembly 36, to a predetermined azimuth position such that when retracted along path 50 the antenna pod 10 may be properly oriented in azimuth against the fuselage or surface 12 of the aircraft in its stowed state. The primary problem with this maneuver of course is that each time the antenna pod structure 10 is to be retracted, it must be remembered to first rotate it to the proper azimuth orientation and then retract it along the translational path 50 to its stowed state. If this initial rotational maneuver is not conducted prior to retraction, the antenna pod structure 10 will not be positioned properly against the aircraft surface 12 in the stowed state which may cause deleterious effects to either the pod structure 10, the surface 12 or both. Thus, to alleviate having to remember to rotate the pod structure 10 prior to each retraction thereof, it would be desirable to have this entire procedure occur automatically during the retraction operation.